The present invention relates to a device in a clamping machine intended for clamping of spring cushion destined for beds, quilts, seats and backs for car seats etc. The spring cushion comprise springs, preferably of screw-shape, which are manufactured of spring wire having circular, square or other section and which are distributed over the whole spring cushion. Extending along the lower edges of the spring cushion is a stiffening member, in most cases in the shape of a metal tape or a flat iron, for example with the dimensions 10.times.1 mm or 6.times.1 mm. The stiffening means defines the contour of the spring cushion and its form in the plane of the spring cushion, e.g. the vertical projection of a seat cushion, by fixing through a clamping operation the lower spring wires extending along the edge to the stiffening member. Extending between the spring cushion stiffening means are transversal spring wires, of which a part extends along the stiffening means and is secured to them by means of clamps.
A machine for clamping spring cushions consists of a plane, horizontal machine table on which the spring cushion rests, and one or more clamping heads disposed along the edges, which heads are fed with clamping strips from a bobbin. The clamping head cuts off a piece of the clamping strip and bends it to a clamp which connects the stiffening means of the spring cushion with spring wires along that edge of the spring cushion which rests on the table. When this side is finished, the spring cushion is reversed entirely, whereupon the stiffening means on the opposite side in a corresponding manner is clamped firmly to the wires.
The clamping head consists of an abutment or dolly part connected with the table and presenting an abutment or dolly groove extending in the longitudinal direction of the stiffening means into which one or more springs of the spring cushion can be introduced to be secured together by means of a clamp. This fixed dolly part is located on the interior side of the edge stiffening means of the spring cushion. Disposed on the exterior side of the stiffening means is a movable attachment head, which presents a longitudinal groove shaped so as to be capable together with the groove of the dolly part to receive and retain the stiffening member and the wires to be clamped together. The attachment head is equipped also with a cutting blade which is in cooperation with a cutting edge for severing a bit of the clamp strip, which thereupon is bent and riveted around the edge stiffening member and the wires. The frame is displaced in the longitudinal direction of the stiffening member and clamps are applied along the stiffening member in desired spacing for joining stiffening members and wires.
The part of the head connected with the table must project upwards above the surface of the table in order to be capable of taking up into its groove the inner part of the stiffening means. This implies that when the frame is displaced in its longitudinal direction the transversal wires cannot pass past the fixed part unless the frame has been raised from the table and over the dolly. The movable part of the head situated on the outer side of the frame can protrude over the surface of the table without constituting any obstacle against displacement of the frame in the direction of the stiffening member.
When using clamping machines with fixed clamping head an automatization of the clamping operation for frames is rendered difficult and even almost impossible. This holds true to a very high degree for frames with irregular contour such as, for example, frames for back seats in cars with interior curvatures for wheel housings, rounded front corners etc.
In known clamping machines the material strip for the clamp is fed through a feeding groove and at the end of the feeding groove there is provided that cutting die which cooperates with the movable part. The construction is shaped so that a redressing of the die is complicated, for instance because the cutting die must be removed for grinding. When using clamping material having varying dimensions, an exchange must be made of parts for the feeding grooves, cutting and feeding devices. Thus must, for example, when working with varying dimensions of the strip or the wires the bending dies always be exchanged.